Mobile electronic devices, including mobile phones, portable music and video players, digital cameras, camcorders, computer peripherals etc. are widely used today. For environmental reasons, such devices are often powered by rechargeable batteries.
There exist a number of methods for charging the rechargeable batteries. As shown in FIG. 1, a first method is to connect the electronic devices 1 to a conventional power line through a power adaptor 2. This method also includes the possibility of removing batteries out of the device and charging them with external chargers, or charging a battery through a USB connection 3 on a PC. No matter what kind of approach is used, the power adaptors and their cables are always cumbersome, and in the case of charging using a USB port, this is restricted by the availability of computers that can be found. Furthermore, the USB port normally can only output a power of 2.5 W which is sometimes lower than the power requirement for recharging and which can cause the charging speed to be slower than a normal battery charger, though it does have the advantage of simultaneous data exchange with the computer at the same time as battery charging.
FIG. 2 shows the pin definition of the connecting port 4 of an exemplary mobile electronic device and its corresponding power/data connector 9. For simultaneous power and data transfer, there are two pins (pin 2 and pin 3) for data connection in addition to the pins (pin 1 and pin 4) used for charging. Many devices have their own charging protocol which needs some predefined voltage level at the data pins to start or continue on charging. For example, some devices need pin 2 and pin 3 to have voltage of 3 V and 2 V, respectively, so that the charging process can be maintained. This requirement can be easily met if the device is charged through a USB port because the data pins can be controlled by the computer. However, when such a device is charged by using a power adaptor 2, a voltage divider as shown in FIG. 2 must be used to provide the required voltage level for data pins.
To get rid of the power wire or the USB connector one possible solution is to use an inductive battery charging platform examples of which are disclosed in U.S. Pat. No. 7,164,255B and US20070029965A. As shown in FIG. 3, the mobile electronic device is inductively coupled with a charging platform 5 which eliminates the need for charging cables to the device. The charging platform 5 is provided with one or more primary windings that generate a magnetic flux that can be picked up by a secondary winding 6 which may be provided integrally with the electronic device. For example, the electronic device may be provided with an inductive energy receiving unit (IERU) 7 which includes the secondary winding 6 and the associated processing circuitry 8 as shown in FIG. 4.
As shown in FIG. 4, an energy receiving winding or coil 6 receives magnetic flux from the charging platform, and the received AC energy is rectified and regulated to a suitable DC voltage to charge the battery. In the prior art it is known that the IERU 7 may be integrated into the device or into the battery pack (US20070029965A) and this is the best approach for future devices. Also known is that the IERU 7 may be integrated into a new back cover for a device which may be used to replace the original (US20060061326A, US20060205381A).
However, there is a need to enable existing devices that are not provided with such an integral IERU—or devices where it is difficult to provide an integrated IERU—to be charged using such an inductive charging platform. One solution to this is to provide the IERU in an external module which is attachable to the back of the device (GB2399466B, US20060205381A). The output of IERU is connected to the connecting port of the device through a short wire or through a power connector. This is a straightforward approach to adapt conventional devices to the charging platform. However, the added module is an extra ‘burden’ to the devices, which has no other function or attraction to a consumer.